1. Field of the Invention
The present invention relates to high power bus assemblies for converters with high speed switches that are modulated to convert electrical power from AC to DC, or from DC to AC.
2. Description of Related Art
There are many instances in which conversion between AC electrical energy and DC electrical energy is useful. For example, U.S. Pat. No. 5,083,039 to Richardson, et al., describes a variable speed wind turbine that utilizes a converter to convert the generated variable frequency AC power to DC power. A second converter then converts this DC power back to fixed frequency AC power that is compatible with the power grid. The converters described therein are switching converters that include a plurality of high speed switches controlled by pulse width modulation techniques to provide either a current-controlled waveform or a voltage-controlled waveform.
High modulation speeds allow greater control of the predetermined waveform; however, modulation speeds are limited by the impedances of the input buses and the output buses. Particularly, an inductive bus impedance substantially attenuates the high frequency bus response at high frequencies, resulting in slower effective switching speed, reduced conversion efficiency, and less accurate waveform control. Another problem related to an inductive impedance is the possibility of damage to the semiconductor devices caused by voltage transients during high speed switching. By reducing the characteristic impedance of the bus, voltage transients can be lowered, thus reducing the potential for damage to the semiconductor devices and increasing their expected lifetime.
To reduce impedance at high (microwave) frequencies, parallel plate transmission lines have been used extensively. For low power electrical circuits, space and cost savings have been realized by using laminated circuits that have a stack of conductive layers alternating with dielectric layers.
High power electrical circuits have power transfer requirements that make implementation with laminated circuits difficult. Particularly, high power conductors require a large conductive cross-section, which requires that the conductors have much greater thicknesses. Furthermore, to avoid arcing, closely positioned high voltage conductors must be well insulated from each other. Arcing is a particular problem when connecting conductors that are in different layers, particularly if the connector passes through another conductive layer.
It would be an advantage to supply a coupler for coupling between layers of a high power laminated bus with low impedance in a compact, robust package that is mechanically strong and can safely and efficiently conduct large current at high voltages.